Sensors which detect the air mass of the air flowing in the intake manifold of the internal combustion engine, so-called air mass flow sensors, are frequently used in the intake manifold to optimize the combustion process of internal combustion engines, for example in motor vehicles. In addition to the intrinsic measuring accuracy of the sensor or the sensor element which is used, and in addition to the further detection of properties of the flowing air mass, such as the temperature or the humidity, the accuracy of the air mass determination also depends on the installation situation of the air mass flow sensor. Here in particular the angular orientation of the air mass flow sensor relative to the air mass flow to be detected plays a decisive role. The more precisely the angle of the air mass flow sensor with respect to the air mass flow agrees during installation into the intake manifold with the setpoint angle for which the sensor measuring values have been calibrated, the more reliable is the determined air mass, and the better may the combustion behavior in the internal combustion engine be optimized.
At the same time, it is frequently necessary in practice to configure the air mass flow sensor configured as a plug-in element into the intake manifold in such a way that the air mass flow sensor may be plugged in together with the intake manifold in a short time and in what may be a simple manner during production. For this purpose, the air mass flow sensor is frequently plugged into a through-passage of the intake manifold, the dimensions of the through-passage being deliberately configured to be greater on all sides than the outer contour of the air mass flow sensor to thus make it easier to plug in the air mass flow sensor. During assembly, the air mass flow sensor is plugged into the intake manifold through the through-passage and, at the end of the plug-in process, an attachment area situated on the air mass flow sensor makes contact with a base of the intake manifold. There, the sensor is then connected to the attachment base, for example, by a screw joint of the attachment area. A sealant situated between the attachment section and the attachment base ensures fluid-tight sealing. However, since the through-passage has a larger dimension than the outer contour of the air mass flow sensor, it is possible for the air mass flow sensor to be variably rotatable regarding its setpoint angular position with respect to the air mass flowing in the intake manifold, and is thus subject to relatively large production fluctuations or production tolerances with respect to its setpoint angular position. As a result, the air mass becomes less accurately detectable. The deviation from the setpoint angular position may thus be up to 2°, or even 2.5°, regarding a rotation about the z-axis extending in the plug-in direction.
An air mass flow sensor system is known from U.S. Pat. No. 7,805,990 B2, in which the assembly of the air mass flow sensor is to be ensured with what may be small production tolerances regarding the setpoint angular position in the intake manifold by using multiple guide notches offset from each other in the outer area of the attachment base. Guide pins, which correspond to the guide notches and are situated on the attachment area of the air mass flow sensor, engage in these guide notches, whereby the air mass flow sensor is to be situated in its correct angular position in the intake manifold.
However, it has been found that such guide notches on the attachment base create a contour on which other objects may become entangled. Similarly, the guide pins projecting from the attachment area of the air mass flow sensor in the plug-in direction may become damaged during handling or during transport, so that they are no longer able to fulfill their function, or other objects may become entangled in these projecting guide pins.